Mammography systems are used for carrying out breast examination of patients using X-rays. An image is acquired using an image receiver which is either a photographic plate or digital sensing means. Such systems are used for taking cranio-caudal and lateral views. A cranio-caudal image comprises irradiating the breast from above so as to obtain a view thereof in an axis running from the head to the feet of the patient. When taking a lateral view, the breast is irradiated from the side in order to obtain a view thereof in an axis passing through the patient's body. Existing mammographs provide various positions for obtaining such views: the patient may be in a sitting, standing, forward leaning or prone position. The prone position is preferred for examinations that also involve a biopsy.
The Italian company IMS Srl is selling a mammograph under the name Ghiotto Hi-Tech which can be used for examinations in the standing or leaning positions as well as for examinations in the prone position. In the prone position, the unit is supplemented by a specialized table. The equipment comprises a crown inside of which an X-ray delivery head and image receiver are rotatively mounted. The delivery head contains those elements necessary for delivering X-rays: source, collimator, filters, etc. The image receiver is associated with a system for compressing or mechanically maintaining the organ to be examined in position. The delivery head and image receiver are located at diametrically opposite points on the crown. The delivery head and image receiver may simultaneously rotate on the crown: they consequently rotate in the plane of the crown about an axis perpendicular to the latter plane, passing through the center of the crown. The crown itself pivots about a horizontal axis passing through one of its diameters. For examination in the standing or leaning position, the crown is in a vertical or oblique plane. When it is desired to take a cranio-caudal image, the delivery head is located at the top of the crown and the image receiver at the bottom. When taking a side view, the crown is rotated so that the delivery head is at the side of the crown. For examination in the prone position, the crown is in a horizontal plane. When taking a cranio-caudal image, the delivery head is located on an axis of extension of the patient's body. To take a side view, the crown is rotated so that the delivery head is at the side of the patient. The disadvantage of this system is that it is necessary to change the patient's position when switching from a cranio-caudal image to a side view. Indeed, rotation by one quarter of a revolution of the crown causes the image receiver to change position on the crown. Access to the patient is also rendered difficult by the presence of the crown.